stimulation of a particular sensory nerve provides codes for that sense no matter how stimulation takes place (ex. pressure on eye)

temporal code

changes in the timing of firing

spatial code

location of firing neurons relative to others

absolute threshold

the minimum amount of stimulus energy that can be detected 50% of the time

subliminal stimuli

stimuli too weak or brief to be perceived

supraliminal stimuli

stimuli that fall about the absolute threshold and are consistently perceived

signal-detection theory

predicts how and when a signal will be detected amid background noise

sensitivity

-the ability to detect a stimulus from background noise
-influenced by intensity of signal, capacity of sensory system, amount of background noise

response criterion

-internal rule used to decide whether or not to report a stimulus
-affected by motivation, wants, needs, and expectancies (ex. airport security)

just-noticeable difference

-the smallest detectable difference in stimulus energy that can be detected 50% of the time
-the weaker the stimuli, easier to detect small differences

Weber's Law

-the more intense the stimulus, the greater the increase in stimulus intensity required for the increase to be perceived
-two stimuli must differ by a constant minimum percentage, rather than a constant amount

Light-electromagnetic radiation

-visable light
-electromagnetic radiation of a wavelenght between 400 and 750 nanometers
-does not need a medium to pass through

-cornea (light enters the curved, transparent, protective layer)
-pupil (light passes through an opening in the eye)
-iris (adjusts the amount of light allowed into the eye)
-lens (lies behind the pupil and bends light rays, focusing them on the retina)
- retina (surface at the back of the eye where light rays are focused)

-has only one pigment
-distributed throughtout the retina, except at the fovea
-faciliatate peripheral vision
-mediate nighttime vision
-receive all colors as shades of gray

cones

-concentrated in center of the retina at the fovea
-mediate daytime vision
-mediate color vision
-provide a sharper image than rods

interactions in the retina

-rods and cones synapse with bipolar cells
-following this, it synapses with ganglion cells
-axons of the ganglion cells gather together to form the optic nerve (carries visual impulses from the retina to the brain)

trichromatic theory

-3 types of color receptors that are each receptive to a different primary color (red, blue, green)
-the ration of the activites of the 3 types of cones indicate what color will be sensed
-color vision is coded by the pattern of activity of the different cones

opponent-process theory

-3 distinct receptors (red green, yellow blue, white black)
-each element signals one color or the other, but never both
-gray results when lights of the 2 colors are mixed together
-supported byt he phenomenon of negative afterimages

trichromats

-people with normal color vision
-have 3 distinct visual pigments

dichromats

-lack one of the 3 pigments
-most are red green blind

monochromats

-have no color vision
-receive visual info through rods only

sex linked recessive trait

-associated with a gene on the X chromosome
-males are more prone to color blindness than females

sound

-repetitive fluctuation in the pressure of a medium like air
-vibrations produce the fluctuations in pressure that constitute sound
-Speech (vocal cords produce vibration into the air, creates waves)

Optic nerve

blind spot

optic chiasm

-half the fibers cross over to the opposite side of the brain
-info from the inner (nasal) half of the retina cross to the opposite side of the brain
-info from the outer (temporal) half of the retina remain on same side
-info from both eyes reaches both sides of the brain
-visual info transmitted to thalamus and then to primary visual receiving area in occipital lobe

-number of complete waveforms that pass by a given point in space every second
-measured in hertz (Hz)

amplitude

-intensity
-difference between peak and baseline of a waveform

pinna

-the crumpled part
-funnels down through the ear canal
-sound waves collect in outer ear

tympanic membrane

-eardrum
-sound waves cause eardrum to vibrate

ossicles

-hammer, anvil, stirrup
-amplify changes in pressure

oval window

-membrane that seperates middle and inner ear
-vibration is up to 90 times greater at this point

cochlea

-amplified vibration transmitted to fluid in the cochlea
-movement of fluid in the cochlea bend the auditory receptor cells (hair cells)
-results in neural impulses in the adjacent auditory nerve
-nerve transmits signals through the medulla and thalamus to the auditory cortex of the temporal lobe

Place theory

-describes a spatial code for frequency
-proposed that pitch is determined by the part of the basilar membrane stimulated
-explains the ability to perceive high frequency tones, but does not explain the ability to perceive lower ones

-nervous system can process only a limited amount of sensory info at any one time
-when too much info is being received, cell sin the spinal cord act as a gate, blocking some pain signals
-ex. massaging area, distracting activity, hot or cold, can reduce pain

referred pain

-pain sensation in one part of the body is perceived as coming from another part

phantom pain

-pain sensation felt in missing limb

taste

-taste buds are the receptors, grouped together in stuctures called papillae
-10,000 taste buds in mouth
-discriminates between sweet, salty, sour, bitter, umami (enhances other tastes), and astringent (produced by tannins, tea)
-each taste bud responds best to 1-2 of these categories

sweet and bitter

signaled when chemicals fit into specific receptor sites

sour and salty

more direct effects on the ion channels in membranes of taste buds

flavor

-smell and taste converge to produce flavor
-food tastes good due to olfactory system more so than the taste system
-olfactory and taste pathways converge in the orbitofrontal cortex, where they also respond to sight and texture of food

olfaction

-sense odor in upper part of nose
-odor molecules readch olfactory receptors by either passing directly through the nostrils or rising through an opening in the palate
-molecules bind to dendrites in the nose, which leads to action potentials

proprioception

allow us to know the position of body and what each part is doing

vestibular sense

-provides info about the position of the head in space and its movements
-sense of balance
-vertigo

vestibular sacs

-organs in the inner ear that connect the semicircular canals and the cochlea
-contribute to the body's sense of balance

semicircular canals

tubes in the inner ear whose fluid, when shifted by head movements, stimulates nerve cells

vestibular system has neural connections:

-cerebellum (helps coordinate body movement
-digestive part of ANS (responsible for nausea)
-muscles of the eye (create vestibular-ocular reflexes (when head moves in one direction eyes more in opposite direction, allows us to fixate on one point))

perception

the process through which sensations are interpreted, using knowledge experience, and understanding of the world, to create meaningful experiences

bottom up processing

-aspects of recognition that depend of the info about the stimulus that comes up to the brain from the sensory receptors
-certain cells respond to certain stimuli
-the brain then recombines this data to create the perceptual experience
-certain features are more important than others (rely on large scale features, such as hair and head shape)

top down processing

-use knowledge in making inferences to recognize objects, especially when sensory info is vague
-experiences creat schemas, which then can bias our perception
-can create a perceptual set, a predisposition to perceive a stimulus in a certain way
-makes educated guesses (can lead to wrong conclusions)

network processing

-utilize both top down and bottom up processing
-parallel distributed processing models (various elements of the object are believed to be simultaneously analyzed by a number of widely distributed, but connected, neural units in the brain. Units work in parallel)

-Voluntary control (purposely focus attention in order to perform a task, reflects top down processing, overt orienting)
-Involuntary attention (bottom up process, abrupt changes in lighting or movement, covert orienting)

-easy if one task is automatic
-more difficult if both require attention (but if tap different kinds of attentional resources, it is possible)
-if 2 tasks require same kind of attention, performance on both tasks will be poor